INSULIN THERAPY IN TYPE 2 DIABETES
InItIatIon, Impact on lIver fat, role of combInatIon therapy wIth
glItazones or glInIdes
Leena Juurinen
ACADEMIC DISSERTATION
To be presented with the permission of the Faculty of Medicine of the University of Helsinki, for public examination in Lecture Hall 4,
University Hospital Helsinki, Haartmanninkatu 4, on May 16th 2014, at 12 o`clock.
Helsinki 2014
Minerva Foundation Institute for Medical Research University of Helsinki
Faculty of Medicine Department of Medicine
Division of Diabetes
Division of Diabetes Helsinki University Hospital University of Helsinki Helsinki, Finland
revIewers Docent Saara Metso, MD, PhD
Unit of Endocrinology, Department of Internal Medicine Tampere University Hospital and
Medical School, University of Tampere Tampere, Finland
and
Professor Jussi Pihlajamäki, MD, PhD
Department of Public Health and Clinical Nutrition University of Eastern Finland
Department of Clinical Nutrition and Obesity Center Kuopio University Hospital
Kuopio, Finland
offIcIal opponent Docent Kirsi A. Virtanen, MD, PhD Turku PET Centre
Turku University Hospital University of Turku Turku, Finland
ISBN 978-952-10-9874-1 ISBN 978-952-10-9875-8 (PDF) Http://ethesis.helsinki.fi
Unigrafia Helsinki 2014
ABSTRACT
aIms
The overall aims of the present studies were to understand the role of the liver in regulating the response to anti-hyperglycemic treatment, and to find ways to optimize basal insulin therapy in patients with type 2 diabetes. Specifically, we determined whether i) insulin therapy changes liver fat content (LFAT) or hepatic insulin sensitivity (I), ii) a peroxisome proliferator-activated receptor gamma (PPARγ) agonist decreases insulin requirements, hepatic insulin resistance and LFAT in patients using high doses of insulin (II), iii) adding nateglinide decreases postprandial glucose excursions (PPGEs) in patients treated with the combination of basal insulin and metformin (MET) (III), iv) insulin can be started in groups as well as individually (IV).
subject and methods
In study I, 14 patients with type 2 diabetes treated with MET alone received additional basal insulin for 7 months. Liver fat content (by proton magnetic resonance spectros- copy, 1H-MRS), fat distribution (magnetic resonance imaging, MRI), fat-free mass and fat mass, whole body and hepatic insulin sensitivity (6-h euglycemic hyperinsulinemic clamp combined with infusion of [3-3H]-glucose), and substrate oxidation rates (indi- rect calorimetry) were measured. In study II, we determined the effect of the PPARγ agonist rosiglitazone (8 mg/d) for 8 months on liver fat and directly measured hepatic insulin sensitivity in 14 patients with type 2 diabetes, who were poorly controlled, i.e.
HbA1c (8.9 ± 0.4%) despite using high doses of insulin (1.98 ± 0.2 IU/kg) in combina- tion with MET. In study I and II, liver fat content (1H-MRS), hepatic insulin sensitivity [6 h hyperinsulinemic euglycemic clamp (insulin 0.3 mU/kg∙min) combined with infu- sion of [3-3H]-glucose], body composition (MRI), substrate oxidation rates (indirect calorimetry), clinical parameters, and liver enzymes were measured before and after additional basal insulin (I) and rosiglitazone treatment (II). Study III was an inves- tigator-initiated, double-blind, randomized, parallel-group study in the five centers.
Patients with type 2 diabetes (n = 88, age 56.0 ± 0.9 years, duration of diabetes 9.4
± 0.5 years, HbA1c 7.8 ± 0.1 %) treated with basal insulin and MET entered a 24-week period, during which basal insulin was titrated to optimize glucose control. Thereafter, the patients were randomized to receive either nateglinide (120 mg three times daily) or placebo for 24 weeks HbA1c, the episodes of hypoglycemia, diurnal glucose pro- files and postprandial glucose excursions were recorded. Study IV was a randomized (1:1), multicenter, two-arm, parallel design study with 3 to 14-week run-in phase and
4–8 or individually, using the same personnel and education program. The patients visited the treatment center before and at the time of insulin initiation and at 6, 12, and 24 weeks. Patients self-adjusted the insulin dose to achieve a fasting plasma glucose target of 4.0–5.5 mmol/l. Glycemic control, the episodes of hypoglycemia, treatment satisfaction, and time spent on patient education were measured.
results
Insulin therapy decreased significantly LFAT (-20 %), and enhanced hepatic insulin sensitivity. Insulin requirements correlated with LFAT. The change in LFAT was sig- nificantly correlated with that in hepatic insulin sensitivity. Rosiglitazone significantly improved glycemic control, decreased liver fat (by 46 %) and insulin requirements (by 41 %), and enhanced hepatic insulin sensitivity. The change in liver fat correlated with the decrease in HbA1c, and improvement in hepatic insulin sensitivity. Nateglinide added to basal insulin and MET slightly but significantly decreased HbA1c due to a decrease in postprandial glucose as compared to placebo. In the study comparing methods to initiate basal insulin, HbA1cdecreased from 8.7±0.2 to 6.9 ±0.1 % in those starting insulin therapy individually and from 8.8±0.2 to 6.8±0.1 % in those starting insulin in groups (not significant [NS]). Insulin doses averaged 62±5 IU and 56 ± 5 IU at 24 weeks (NS), respectively. The frequency of hypoglycemia was similar in booth groups. The total time (visits and phone calls) spent in initiating insulin in groups was 48 % less than in those treated individually. Diabetes treatment satisfaction improved similarly in both groups.
conclusIons
In conclusion, insulin therapy has favorable effects on the liver as it improves hepatic insulin sensitivity and significantly reduces liver fat content. Rosiglitazone decreases liver fat content and enhances hepatic insulin sensitivity. Addition of a short-acting insulin secretagogue slightly but significantly improves postprandial hyperglycemia during combination therapy with basal insulin and MET. Similar glycemic control and treatment satisfaction can be achieved by initiating insulin in groups and individually but initiation in groups takes half as much time as individual initiation.
CoNTENTS
abstract ... 3
lIst of orIgInal publIcatIons ...………...………... 7
abbrevIatIons ………... 8
1. IntroductIon ... 10
2. revIew of the lIterature ………... 12
2.1. PATHOGENESIS OF TYPE 2 DIABETES ………... 12
2.1.1. Insulin resistance, the MetS and NAFLD ………... 12
Definitions ... 12
Methods to measure insulin sensitivity ………. 12
Insulin resistance in the liver ……… 13
Regulation of liver fat in humans ……… 14
Insulin resistance in adipose tissue ... 15
Insulin resistance in skeletal muscle ... 16
Defects of insulin action in other tissues ……….. 16
2.1.2. Defects in insulin secretion ……… 17
2.2. TREATMENT OF HYPERGLYCEMIA IN TYPE 2 DIABETES ………... 17
Treatment targets and effects of insulin therapy on micro- and macrovascular disease ……… 17
2.2.1. Weight loss and exercise ………... 17
2.2.2. Oral agents and GLP-1-analogues ... 18
Metformin ………... 18
Sulfonylureas ………... 18
Glinides ………... 19
Glitazones ………... 19
DPP-4- inhibitors ... 20
GLP-1 - analogues ………... 20
SGLT-inhibitors ………... 21
2.2.3. Insulin ... 22
Choice of the insulin regimen ……… 22
Practical aspects of initiation of insulin therapy .………. 24
3. aIms of the study ………... 25
4.1 Subjects ... 26
4.2 Study designs ... 27
5. methods ... 31
5.1. Hepatic insulin sensitivity (I, II) ………... 31
5.2. Liver fat content (I, II) ………... 32
5.3 Measures of body composition (I, II) ………... 33
5.4 Measurements of substrate oxidation rates (I, II) ………... 33
5.5 Transthoracic echocardiography (II) ………... 34
5.6 Optimization of insulin therapy (III, IV) ………... 34
5.7. Analytical procedures ………... 35
5.8. Statistical analyses ………... 36
6. results ... 38
6.1. Effect of insulin therapy on liver fat content and hepatic insulin sensitivity in patients with type 2 diabetes (I) ……….... 38
6.2. Liver fat content and hepatic insulin sensitivity after combination of rosiglitazone to metformin and insulin therapy (II) ... 43
6.3. Postprandial hyperglycemia after combination of nateglinide to metformin and insulin therapy (III) ………... 44
6.4. Initiation of insulin therapy individually or in groups (IV) ……... 48
7. dIscussIon ………... 51
8. summary and conclusIons ...…...………... 56
9. acKnowledgements ... 57
10. references ………... 59
orIgInal publIcatIons ... 74
LIST oF oRIGINAL PUBLICATIoNS
thIs thesIs Is based on the followIng publIcatIons, whIch are referred to the text by theIr roman numerals.
I
Juurinen Leena, Tiikkainen Mirja, Häkkinen Anna-Maija, Hakkarainen Antti, Yki-Järvinen Hanneleeffects of insulin therapy on liver fat content and hepatic insulin sensitivity in patients with type 2 diabetes.
American Journal of Physiology, Endocrinology and Metabolism 292:
E829–E835, 2007.
II
Juurinen Leena, Kotronen Anna, Granér Marit, Yki-Järvinen Hannele rosiglitazone reduces liver fat and insulin requirements and improves hepatic insulin sensitivity and glycemic control in patients with type 2 diabetes requiring high insulin doses. Journal of ClinicalEndocrinology and Metabolism 93: 118–124, 2008.
III
Juurinen Leena, Tiikkainen Mirja, Saltevo Juha, Nikkilä Katriina, Lanki, Helena, Leppävuori Eeva, Kock Tuula, Teikari-Myyrä Tarja, Kauppinen-Mäkelin Ritva, Kotronen Anna, Yki-Järvinen Hannele nateglinide combination therapy with basal insulin and metformin in patients with type 2 diabetes. Diabetic Medicine 26: 409–415, 2009.Iv Yki-Järvinen Hannele, Juurinen Leena, Alvarsson Michael, Bystedt Tord, Caldwell Ian, Davies Melanie, Lahdenperä Sanni, Nijpels Gil,
Vähätalo Markku
Initiate Insulin by aggressive titration and education (InItIate):
a randomized study to compare initiation of insulin combination therapy in type 2 diabetic patients individually and in groups.
Diabetes Care 30: 1364–1369, 2007.
Publication II has also been included in the doctoral thesis of Anna Kotronen entitled liver fat in the metabolic syndrome and type 2 diabetes, University of Helsinki, 2008.
ABBREVIATIoNS
ALP alkaline phosphatase ALT alanine aminotransferase AST aspartate aminotransferase ANOVA analysis of variance
BMI body mass index
CoA coenzyme A
DAG diacylglycerol
DNL de novo lipogenesis DPP-4 Dipeptidyl peptidase-4
DQTS diabetes treatment satisfaction questionnaire EGP endogenous glucose production
FDG fluorodeoxyglucose FFA free fatty acids
fm fat mass
ffm fat free mass
FPI fasting plasma insulin
fP fasting plasma
FPG fasting plasma glucose
fS fasting serum
GAD glutamic acid decarboxylase GLP-1 glucagon like peptide-1 GLUT4 glucose transporter 4 GCP good clinical practice HDL high density lipoprotein HbA1c glycosylated hemoglobin A1c HGP hepatic glucose production
1H-MRS proton magnetic resonance spectroscopy
HOMA-IR homeostasis model assessment of insulin resistance
IA intra-abdominal
IFG impaired fasting glucose IGT impaired glucose tolerance IMCL intramyocellular lipid IR insulin resistance LDL low density lipoprotein
LFAT liver fat
LPL lipoprotein lipase
MET metformin
Mets metabolic syndrome
MRI magnetic resonance imaging MRS magnetic resonance spectroscopy NAFLD non-alcoholic fatty liver disease NASH non-alcoholic steatohepatitis NEFA non-esterified fatty acid NPH neutral protamine Hagedorn
NS not significant
OAD oral antidiabetic drug(s) OGTT oral glucose tolerance test PAI-1 plasminogen activator inhibitor 1 PET positron emission tomography
PKC protein kinase C
PPGE postprandial glucose excursion ppm parts per million
PPARγ peroxisome proliferator-activated receptor gamma QUICKI quantitative insulin sensitivity check index
Ra rate of appearance
Rd rate of disappearance
S serum
SA specific activity
SAT subcutaneous adipose tissue
SC subcutaneous
SEM standard error of mean
SU sulphonylurea
TZD thiazolidinedione(s) TAG triacylglycerol(s)
TG triglycerides
VAT visceral adipose tissue VLDL very low density lipoprotein WHR waist to hip ratio
wks weeks
1. INTRoDUCTIoN
Increased fat accumulation in the liver due to non-alcoholic fatty liver disease (NAFLD) is a key feature of the insulin resistance/metabolic syndrome and the most common cause of elevated liver enzymes (1). The liver is the source of glucose and triglycerides (TG), two of the key components of the metabolic syndrome (MetS). The liver, once fatty, becomes resistant to the normal actions of insulin to inhibit the production of glucose and VLDL (2), (3). This leads to hyperglycemia and stimulation of insulin secretion as well as hypertriglyceridemia (2), (4).
Achievement of good glycemic control is a major challenge in the clinic in patients with type 2 diabetes. In Finland it has been estimated that less than 25 % of type 2 diabetic patients achieve the average HbA1c target of 7.0 % often regarded as the goal in treating hyperglycemia (5), (6). This is also true even if insulin therapy is used to control glycemia. One possible reason for this failure is fat accumulation in the liver due to NAFLD. Consistent with the knowledge that the fatty liver is insulin resistant in type 2 diabetes, the amount of insulin needed depends on the amount of fat in the liver (7), (8). However, insulin also directly stimulates lipogenesis in the liver (9) raising the possibility that insulin therapy actually worsens hepatic insulin resistance by increasing liver fat content. Therefore we determined the effect of insulin therapy on hepatic insulin sensitivity and liver fat content.
PPARγ-agonists such as rosiglitazone and pioglitazone increase hepatic insulin sensitivity and lower liver fat content when given as monotherapy to patients with type 2 diabetes (10), (11). In the present study, we examined these drugs are helpful in improving glycemic control particularly in patients who have a high liver fat content and high insulin requirements.
Basal insulin combination therapy is recommended as the regimen of choice in initiating insulin therapy in patients with type 2 diabetes poorly controlled on oral agents alone (6). Although the treatment target of 7.0% can on the average be achieved with basal insulin (12), (13) some patients have residual postprandial hyperglycemia.
A possible option is to treat postprandial hyperglycemia with short-acting insulin regimens, dipeptidyl peptidase-4 (DPP-4)-inhibitors, glucagon like peptide-1 (GLP- 1)-analogues, or glinides. Nateglinide is a derivate of meglitinide, which stimulates insulin secretion (14). In the present study, we examined whether this drug improves postprandial hyperglycemia also when added to basal insulin therapy.
Although basal insulin therapy is a simple and effective way in initiating insulin therapy on an out-patient basis (15), it nevertheless requires a nurse to teach basic skills such as measurement of fasting glucose concentrations and injection of insulin.
This is time-consuming and perhaps limits initiation of insulin therapy. There is thus a need to develop new ways to ease the transition from oral agents to insulin.
The present series of studies were undertaken to improve treatment of type 2 diabetic patients. We examined the effect of insulin and rosiglitazone on hepatic insulin sensitivity and liver fat content and the effect of adding nateglinide on postprandial glycemia in patients treated with basal insulin combined with metformin. We also studied whether the patient education how to start basal insulin therapy can be carried out in patient groups as well as individually.
2. REVIEW oF THE LITERATURE
2.1. pathogenesIs of type 2 dIabetes
2.1.1. InsulIn resIstance, the mets and nafld defInItIons
Insulin resistance is defined as the inability of insulin to produce its biological actions at circulating concentrations that are effective in normal subjects (16). Insulin resis- tance may involve any of the metabolic actions of insulin, a cluster of metabolic and cardiovascular risk factors. The most recent criteria for diagnosis of the MetS are as follows: the presence of any three of the following five risk factors: waist circumfer- ence ≥80 cm in women and ≥94 cm in men, fasting glucose ≥5.6 mmol/l or drug treatment for hyperglycemia, fS-TG ≥1.7 mmol/l or drug treatment for hypertriglyceri- demia, HDL-cholesterol <1.3 mmol/l, women and <1.0 mmol/l, men or drug treatment for low HDL-cholesterol, systolic blood pressure ≥130 mmHg and/or diastolic blood pressure ≥85 mmHg or antihypertensive drug treatment (17).
NAFLD is defined as excess fat in the liver in the absence of excess alcohol abuse (<20g/day) or other causes of liver disease (16). It covers conditions from simple st- eatosis to steatohepatitis (NASH) (18). In NAFLD, liver fat exceeds 10 % as determined by histology (19), and over 5.6 % measured by spectroscopy (20). Liver fat content have been shown to correlate significantly with all features of MetS independent of BMI (1), (21).
methods to measure InsulIn sensItIvIty
The golden standard for measurement of insulin sensitivity is the euglycemic hyper- insulinemic clamp technique (22). With this technique, whole body insulin sensitivity is measured as the amount of glucose required to maintain normoglycemia during intravenously induced hyperinsulinemia (22). Without isotopes, the glucose infusion rate corrected for changes in glucose concentrations, provides a measure of whole body insulin sensitivity but does not allow distinction between hepatic and peripheral insulin resistance (23), (24), (25). To determine the tissue localization of insulin resis- tance (liver vs. periphery), a glucose isotopes needs to be used (25). For the calcula- tion of glucose kinetics the Steele equation is used (26).
Insulin sensitivity in adipose tissue (insulin sensitivity of lipolysis) can be quantified by infusing a radioactive or stable glyserol or free FFA tracer (27), (28). In addition,
PET with 18FDG (fluorodeoxyglucose) can be used to determine glucose uptake in adipose tissue (29), in skeletal muscle (30), (31), and the liver (32).
Other methods to measure insulin sensitivity and glucose metabolism include the intravenous insulin tolerance test (33), the insulin suppression test (34), (35), and the frequently sampled intravenous glucose tolerance test (FSIVGT) with minimal model assessment (36). Methods based on measurement of fasting insulin concentrations, such as fP-insulin, homeostatic model assessment [HOMAIR = (fasting insulin x fasting glucose)/22.5, qualitative insulin check index, [QUICKI = 1/(log fasting insulin+log fasting glucose)] cannot be used to reliably measure insulin sensitivity in type 2 diabetes since it is unclear how well these tests function in subjects with decreased β-cell secretion (37). Fasting insulin also increases because of impaired insulin clearance in subjects with a fatty liver (38). Thus, e.g. HOMA overestimates hepatic insulin resistance compared to insulin resistance in skeletal muscle. The HOMA method is, however used to measure insulin sensitivity in large epidemiologic studies (39).
InsulIn resIstance In the lIver
The liver is mainly responsible for glucose production in the postabsorptive phase (40), (41), (42). Approximately 50–64 % of total hepatic glucose production is due to gluconeogenesis. Insulin inhibits hepatic glucose production (HGP) (23). This occurs both via inhibition of glycogenolysis (43) and gluconeogenesis (44). Insulin also sup- presses HGP via a decrease in glucagon secretion (45). In addition, insulin inhibits the production of VLDL from the liver (46).
Hepatic insulin resistance
Hepatic insulin resistance of glucose production is characterized by a defect in the ability of insulin to suppress HGP (47), (2). A high LFAT content impairs insulin sup- pression of HGP in non-diabetic subjects (2) and in type 2 diabetic patients (7).This leads to an increase in basal HGP in the fasting state (2). Postprandial hyperglycemia is also characterized by persistent HPG after a meal (48). Patients with type 2 dia- betes have more LFAT than non-diabetic subjects for the same BMI (49). LFAT also correlates with insulin requirements in patients with type 2 diabetes (7).
Insulin resistance affects not only glucose but also lipid metabolism in the liver.
The increase in LFAT has been shown to lead to overproduction of VLDL (4) due to a defect in insulin suppression of VLDL production (3). In addition, due to the defect in the antilipolytic effect of insulin, the suppression of FFA by insulin is blunted (2) contributing to increased hepatic uptake of FFA (50).
regulatIon of lIver fat In humans
Overfeeding and weight loss
Excessive energy intake (43 % fat, 45 % calories from carbohydrate, and 12 % from protein) increases liver fat content significantly within four weeks in healthy, nor- mal weight subjects (51). We recently showed that liver fat increased by 27 % in three months by carbohydrate overfeeding when body weight increased only by 2 % (52). Several studies have shown that weight loss markedly decreases LFAT in non-diabetic subjects (53), (54), (55) and in patients with type 2 diabetes (56), (57).
Glitazones
TZDs are PPARγ (peroxisome-proliferator-activated receptor-gamma) agonists. TZDs bind to the transcription factor PPARγ, which regulates gene expression in response to ligand binding. PPARγ is mainly expressed in adipose tissue and slightly also in the liver, in skeletal muscle, in heart, and in endothelial cells and macrophages (58).
PPARγ regulates the transcription of numerous genes involving carbohydrate and lipid metabolism (59) and inflammation (58). TZDs increase hepatic and peripheral insulin sensitivity (60), (61), (10) and have been shown to decrease liver fat content in several studies (60), (61), (62), (10).
The improvement in insulin sensitivity and decrease in LFAT by TZDs are accompanied by a marked increase in serum adiponectin concentrations (63), (10).
In mice, adiponectin, which is produced exclusively in adipose tissue, decreases liver fat content and hepatic inflammation (64). Adiponectin is thus one possible mediator of the beneficial effects of TZDs on the liver. TZDs have reduced steatosis, inflammation, and ballooning necrosis in randomized controlled clinical trials addressing treatment of NASH (61), (65), (66), (67).
During insulin combination therapy in patients with type 2 diabetes, insulin doses vary at least 20-fold from 10 to 200 IU/d (8), (15), (68). In 2000, LFAT was shown to correlate with insulin requirements in type 2 diabetes (7). This suggests that especially patients with high insulin requirements could benefit from therapies such as TZDs, which lower LFAT. However, because of fear of hepatotoxicity after withdrawal of troglitazone due to liver reactions, patients with elevated liver enzymes were carefully excluded from insulin-TZD studies (69), (70), (71), (72), (73), (74). Use of rosiglitazone or pioglitazone has not been accompanied by hepatotoxicity but rather beneficial effects on LFAT, hepatic insulin sensitivity and liver histology (58).
Metformin
We previously compared effects of rosiglitazone and MET on LFAT in patients with type 2 diabetes (10). In a previous study, MET had no effect on LFAT while rosiglitazone decreased LFAT by 51 % (10). The lack of an effect of MET on LFAT as measured by computed tomography in type 2 diabetes was confirmed by Gupta et al (75) and by
Teranishi et al who used 1H-MRS to determine LFAT before and 6 months after MET in 20 Japanese type 2 diabetic patients (76).
Insulin
In patients with NAFLD, lipolysis and de novo lipogenesis are the main sources of excessive intrahepatocellular triglycerides (77). Insulin, even at low concentrations effectively lowers S-FFA and may therefore lower liver fat content (2). On the other hand, insulin stimulates fatty acid and VLDL synthesis in the liver, which could increase LFAT (78). Body weight also increases during insulin therapy in proportion to improved glycemic control (79), while weight loss reduces LFAT (53). There are no studies addressing effects of insulin therapy on liver fat content.
Genetic factors
Genetic factors have been shown to associate with NAFLD (80), (81), (82). The genetic variation in the gene patatin-like phospholipase domain-containing protein 3 (PLPNA3, adiponutrin gene) was found to associate with LFAT (83). The meta-analysis also showed that subjects with NALFD and the I148M variant (rs738409C>G) in PNPLA3 gene not only were in risk for 73 % higher LFAT but also were predisposed to have 3.2-fold risk for NASH and the fibrosis in the liver (84).
InsulIn resIstance In adIpose tIssue
The main function of adipose tissue is to store excess energy in the form of triacylglycerols (TAG). On the other hand, under fasting conditions lipolysis of TAG-stores in adipose tissue releases glycerol and FFA into the circulation for use in other tissues (85). The main regulator of both processes is insulin. Insulin inhibits lipolysis via inhibition of hormone-sensitive lipase (HSL). It also inhibits intravascular lipolysis, i.e. hydrolysis of VLDL and chylomicrons via inhibition of lipoprotein lipase (LPL). Adipose tissue also acts as an endocrine organ. It secretes adipokines, peptide hormones, and cytokines such as adiponectin, leptin, tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6) (86), (87).
Adiponectin is produced exclusively by adipose tissue and appears to act mainly in the liver, where it enhances hepatic insulin sensitivity and decreases inflammation (88), (89).
Adipose tissue insulin resistance is characterized by enhanced lipolysis (90). The increase in circulating FFA decreases insulin-stimulated glucose uptake and the ability of insulin to suppress HGP (91). Adipose tissue lipolysis has been shown to be insulin resistant in obese subjects (92) and patients with type 2 diabetes (49). Adipose tissue insulin resistance correlates with LFAT in obese subjects (93) and in type 2 diabetes (49).
Adipose tissue in obese insulin resistant subjects is inflamed (89). This inflammation is characterized by an increase in the number of macrophages surrounding dead adipocytes (94). Plasma concentrations of adiponectin are low in obesity and in type 2 diabetes (95), in non-diabetic subjects with family history of type 2 diabetes (96),
and in NAFLD (97). The severity of whole body insulin resistance is inversely related to low serum adiponectin concentrations (95).
InsulIn resIstance In sKeletal muscle
After an overnight fast, when serum insulin concentration is low, only ~10 % (25), (98) of glucose utilization occurs in skeletal muscle. Most of glucose is used in the brain and other insulin-independent tissues (25). In healthy subjects insulin stimulates glucose uptake by skeletal muscle (23), (99).
The ability of insulin to increase glucose uptake is impaired in patients with type 2 diabetes (100), (101), (102). Both insulin-stimulated glucose oxidation and non- oxidative glucose metabolism are deteriorated in type 2 diabetes (103), (104). The defect in insulin stimulated glucose disposal is observed in type 2 diabetes when studied under normoglycemic conditions. However, glucose itself is a potent stimulator of glucose uptake (105).When glucose uptake is measured under hyperglycemic conditions mimicing those prevailing under everyday conditions, glucose uptake is similar in type 2 diabetic patients and matched normal subjects (105), (106). In the basal state, when glucose uptake is largely non-insulin-dependent, rates of absolute whole body and muscle glucose utilization are increased in patients with type 2 diabetes compared to normal subjects, in proportion to hyperglycemia (98).
Hyperglycemia (107), (108), or high S-FFA (91), (92), (30), (109) induce insulin resistance in human skeletal muscle. The rate of insulin-stimulated glucose uptake in type 2 diabetic patients is inversely proportional to the degree of chronic hyperglycemia (105). Increases in S-FFA within the physiological range have also been shown to decrease insulin-stimulated glucose uptake and impair insulin signaling (110).
defects of InsulIn actIon In other tIssues
Insulin is known to cause vasodilatation and decrease the stiffness of large arteries (111). Normally insulin inhibits platelet aggregation (112). Insulin stimulates sympathetic nervous system (113) and regulates heart rate (114). Several defects of insulin action in cardiovascular system are found in insulin resistant state, such as the inability of insulin to decrease central aortic pressure in large arteries (111), (115), the defects in endothelium-dependent vasodilatation (116), (117), and in myocardial insulin resistance as measured by PET (118). Insulin action on platelets has shown to be blunted in insulin resistant subjects (112). The action of insulin in central nervous system has been studied using mouse models. Insulin action in brain is supposed to regulate glucose and fat metabolism, and central insulin resistance may lead to insulin resistance in other tissues (119).
2.1.2. defects In InsulIn secretIon
The insulin response to intravenous glucose is biphasic. An early first-phase burst is followed by a second, sustained phase. Glucose tolerance deterioration from normal to impaired means a progressive decrease in the acute insulin response to glucose (120), and an increase in the response of total insulin to oral glucose load (121). Despite this, most patients with type 2 diabetes are hyperinsulinemic (122).
The increase in total insulin concentrations is an attempt of β-cells to maintain normal glucose tolerance. Once the 2-h plasma glucose in an oral glucose tolerance test (OGTT) exceeds 11.0 mmol/l, insulin secretion starts to decrease relative to insulin resistance and hyperglycemia (122). This means the onset of type 2 diabetes. There is thus absolute hyperinsulinemia but relative deficiency of insulin in type 2 diabetic patients.
The defects in insulin secretion may be familial, inherited or acquired. Poly- morphisms in genes involved in insulin secretion seem to be more common in patients with type 2 diabetes than in non-diabetic subjects. Identification of these genetic markers has not, however, helped in identification of subjects at risk of developing type 2 diabetes (123). Acquired factors such as gluco- and lipotoxicity, and amyloid deposition may also contribute to β-cell exhaustion (124), (125), (126).
2.2. treatment of hyperglycemIa In type 2 dIabetes
Treatment targets and effects of therapy on micro-and macrovascular disease Lowering of HbA1c below 7.0 % has been shown to decrease the risk of microvascular disease (6). This goal therefore has been recommended as an average HbA1c target for patients with type 2 diabetes. On the other hand, the treatment target should be defined individually after considering hypoglycemia, age, and the presence of complications. Long-term follow-up of patients in the UKPDS, where sulphonylureas, metformin and insulin were used as antihyperglycemic agents suggested that intensive glucose control may be beneficial also for the prevention of macrovascular disease (6), (127).
2.2.1 weIght loss and exercIse
Obesity and sedentary lifestyle together with genetic susceptibility are main reasons for deterioration of glucose metabolism. Lifestyle intervention such as weight reduction, healthy diet and increased physical activity have shown to decrease the risk of diabetes (128). In addition, the changes in lifestyle can reduce the risk of type 2 diabetes in subjects with impaired glucose tolerance (129). Several studies have shown that dietary changes resulting in weight loss decrease HbA1c (130), (131), (132), (133). Bariatric
surgery reverses type 2 diabetes in 36 % when assessed 10 years after gastric by- pass surgery (134).
Daily physical activity associates closely to insulin sensitivity in non-diabetic subjects (135). Whole body insulin sensitivity correlates closely with maximal aerobic power (VO2max). Aerobic exercise, already within one week, improves significantly peripheral insulin sensitivity in subjects with type 2 diabetes (136). Both diet and exercise have shown to decrease HbA1c similarly in patients with type 2 diabetes (137).
Aerobic training together with high-intensity resistance training have decreased HbA1c by approximately 1.0–0.7% (138), (139), (140) in type 2 diabetes.
2.2.2 oral agents and glp-1 -analogues
Metformin
MET, a biguanide, the first-line therapy in type 2 diabetes (6) has been is used over 40 years. MET decreases the rate of HGP (141), (142), (10). This is mainly due to the decrease in gluconeogenesis (143). MET promotes weight loss (141) which may improve whole body insulin sensitivity. MET has been reported to decrease serum lipids, especially TG concentrations (144), (143). The risk of lactic acidosis, a serious adverse effect of MET, is very low (145). MET has shown to decrease HbA1c approximately 1.5%
(144) without increasing the risk of hypoglycemia (146), (145).
MET has been shown to prevent type 2 diabetes (147) and to reduce the risk of cardiovascular diseases (146) (127). Furthermore, MET may decrease the risk of cancer in patients with type 2 diabetes (148), (149).
Sulfonylureas
Sulfonylureas (SUs) stimulate insulin secretion by closing ATP dependent K+-channels in beta cells (150). SUs bind to the β-cell sulphonylurea receptor -1, which forms a transmembrane complex together with Kir 6.2 potassium channels. Reduced potassium efflux leads to cascade of the membrane depolarisation, opening of Ca2+ channels, and the activation of calcium-dependent proteins controlling insulin release (151).
SUs have been shown to decrease HbA1c by ~1–2% (144). The efficacy depends on the adequacy of the beta-cell function (152). Within five years, however, the glycemic control has shown to deteriorate in patients treated with SU (153). Weight gain and hypoglycemia (153), concerning especially elderly individuals and patients with renal insufficiency (154) are the main adverse effects of SU. Since SU are bound to plasma proteins, interaction with other drugs, such as salicylates, warfarin, and sulphonamides, may lead to the increase in the risk of hypoglycemia (155).
Glinides
Derivates of meglitinide, such as repaglinide (carbamoylmethyl benzoic acid derivate) and nateglide (D-phenylalanine derivate), stimulate the release of insulin from β-cells, and nateglide is eliminated primarily by kidney (156) and repaglinide via the biliary tract. The absorption and the elimination are rapid. Both of these short-acting insulin secretagogues have been shown to decrease postprandial hyperglycemia (157), (158).
The meal-related dosing of repaglinide has been shown to decrease HbA1c by ~1 % (159). The effect of nateglinide vs. placebo on HbA1c in various studies in type 2 diabetic patients has been summarized in table 1. The geometric mean change by nateglinide vs. placebo in the studies in Table 1 has averaged 0.5 %.
Glinides increase the risk of hypoglycemia but less than long-acting sulphonylureas (14). The percentage of patients reporting hypoglycemia was 3 % for nateglinide compared to 14 % for glyburide (14). In a 24-week study performed in 675 type 2 diabetic patients confirmed hypoglycemia occurred in 5.3 % of the patients treated with nateglinide (160). Whether glinides are helpful in improving glycemic control in patients treated with basal insulin – MET combination therapy has not been examined.
In study IV, we hypothesized that addition of nateglinide to basal insulin combined with MET might help in controlling postprandial hyperglycemia in type 2 diabetes.
table 1. The effect of nateglinide as compared to placebo on glucose control in drug-naïve patients with type 2 diabetes.
Author AuthorAuthor Author Reference Reference Reference Reference nnnn
Study Study Study Study Duration Duration Duration Duration
(wks) (wks) (wks) (wks)
Basal Basal Basal Basal HbA1c HbA1c HbA1c HbA1c (%) (%) (%) (%)
Nateglinide Nateglinide Nateglinide Nateglinide
HbA1c HbA1c HbA1c HbA1c
(%)(%)(%)(%)
Placebo Placebo Placebo Placebo
HbA1c HbA1c HbA1c HbA1c
(%)(%)(%)(%) p pp p----valuevaluevaluevalue
Horton ES
161 701 24 8.3 -0.5 0.5 <0.001
Hanefeld M
162 289 12 8.3 -0.55 0.07 <0.05
Rosenstock J
163 585 16 8.4 -0.6 0.5 <0.001
Saloranta C
160 334 24 6.6 -0.39 0.16 <0.001
Mari A
164 108 24 6.6 -0.31 -0.1 NS
Schwarz SL
165 52 12 7.6 -0.7 -0.2 0.004
Glitazones
TZDs are insulin-sensitizers enhancing whole body insulin sensitivity (166), (167), (142) hepatic insulin sensitivity (10) and adipose tissue insulin sensitivity (60). TZDs increase the suppression of HGP by insulin (166) and decrease HbA1c approximately 1 to 1.5%.
From three TZDs only pioglitazone is in clinical use. Troglitazone was withdrawn due to hepatotoxicity (168) and rosiglitazone due to increase in cardiovascular events, especially heart failure (169). TZDs decrease liver fat content approximately 50%
(10), (11), (60). In the previous studies the combination therapy of insulin and TZDs decreased insulin requirements slightly. Glycemic control improved in spite of the increase in body weight. LFAT was not measured in these studies (69), (70), (71), (72), (73).
TZDs increase the incidence of congestive heart failure (170), (58), (70). In addition, TZDs are associated with weight gain, a small decrease in hemoglobin (171), (167), and fluid retention (58). The reason for fluid retention and peripheral edema may be due to reduction of renal extraction of sodium (172). Pioglitazone and placebo was shown to have similar congestive heart failure related mortality (170) but with rosiglitazone the increase in mortality due to heart failure was shown to be doubled compared to placebo (169). Use of TZDs also increases the risk of fractures (173).
DPP-4 inhibitors
Glucagon-like peptide 1 (GLP-1) is secreted from L-cells in response to a meal and stimulates insulin secretion as well as lowers glucagon secretion (174). Dipeptidyl peptidase-4 (DPP-4) is an aminopeptidase, which postprandially rapidly degrades the incretin hormones, glucose-dependent insulinotrophic polypeptide (GIP) and GLP-1.
DPP-4 is expressed in many tissues, and on the surface of lymphocytes, macrophages, and endothelial cells (175). Inhibition of DPP-4 by DPP-4 inhibitors such as sitagliptin, vildagliptin, saxagliptin and linagliptin, increases the concentration of endogenous active plasma GLP-1 (176), (177).
DPP-4 inhibitors have been shown to decrease HbA1c by ~0.5% from the baseline HbA1c of 7.4% (178), (179), (180), (181). The elimination of DPP-4-inhibitors occurs mainly by the kidney with the exception of linagliptin, which is metabolized mainly by the liver (182). Vildagliptin had no effect on fasting TG or total cholesterol concentrations (183).
DPP-4 inhibitors are well-tolerated, weight neutral and do not cause hypoglycemia (182).
DPP-4 inhibitor linagliptin when added to basal insulin therapy improved glycemic control and HbA1c decreased approximately 0.6 % (184). The frequency of hypoglycemia was low. Similar results are reported with other DPP-4 inhibitors combined to basal insulin therapy (185), (186).
GLP-1 analogues
Oral glucose induces a higher insulin response than intravenous glucose load has been attributed to incretin hormones, GLP-1 and GIP (187). Over 50 % of the glucose- stimulated insulin response is suggested to be due to incretin effect, which is blunted in patients with type 2 diabetes (174). The response of insulin to glucose is decreased due to a resistance of GIP-action and a deficiency of GLP-1 in patients with type 2
diabetes (119). Thus, the lower GLP-1 levels after mixed meal contribute to increase in glucagon secretion leading hyperglycemia (174).
GIP is synthesised in K-cells of the proximal small intestine and GLP-1 in L-cells in the distal ileum and colon (174). They increase insulin secretion in a glucose-dependent manner. Incretins act by decreasing basal and postprandial glucagon secretion, delaying gastric emptying, and increasing satiety. Furthermore, incretins may have beneficial effects on beta cell function (188).
Endogenous GLP-1 has a short half-life due to quick enzymatic deactivation in the circulation by DPP-4. GLP-1 analogues such as exenatide, liraglutide and lixisenatide, are resistant to enzymatic deactivation by DPP-4 (189).
When used as monotherapy GLP-1-analogues decrease HbA1c by ~0.8% (190), (191), (178). Despite improved glycemic control, body weight decreases significantly by 2-4 kg (191). Gastrointestinal side-effects and nausea are common. A low risk of hypoglycemia, weight loss and the efficacy in the combination therapy with other OAD (192) and with basal insulin (193) are the advantages of these drugs for patients with type 2 diabetes.
SGLT-inhibitors
Sodium-glucose cotransporter (SGLT) 2 inhibitors have been recently introduced as antihyperglycemic agents for patients with type 2 diabetes. SGLT2 is expressed at the luminal membrane of proximal renal tubules. SGLT2is the major transporter responsible for glucose reabsorption. SGLT1 reabsorbs the remaining 10% of the filtered glucose.
The average of the daily amount of glucose reabsorbed by the kidney in healthy subjects is around 160 grams of glucose. No glucose normally appears in the urine (194).
Dapagliflozin is an SGLT2 inhibitor. It thereby inhibits reabsorption of glucose and increases urinary excretion, which lowers plasma glucose concentrations. The glucose- lowering effect in patients with type 2 results in approximately a 0.7 % decrease in HbA1c without increasing hypoglycemia when compared to placebo (195). Weight loss by dapagliflozin was approximately 3 kg in 24-week placebo-controlled study.
The adverse events, such as signs and symptoms of urinary infections and genital infections, were more common in group treated with dapagliflozin as compared to placebo (195).
Author (Reference) Author (Reference)Author (Reference)
Author (Reference) ComparatorComparatorComparatorComparator with OAD with OAD with OAD with OAD
ENDHbA ENDHbA ENDHbA ENDHbA1c1c1c1c
%
%
%
%
HbAHbAHbAHbA1c1c1c1c
%
%
%
%
ID ID ID ID IU/kg, IU/day IU/kg, IU/dayIU/kg, IU/day IU/kg, IU/day
WeightWeightWeightWeight kg kg kg
kg HypoglycemiaHypoglycemiaHypoglycemiaHypoglycemia
Kilo et al (196) NPH+MET, n=91 Bas.1c 9.5 %
MIX30+MET 8.3 / 8.2 (NS) 1.2 / 1.3 (NS) 28 / 26 (ND) 0.1 / 0.7(NS)
0.55 / 1.04 13 % / 24 %
(ND)
Malone et al†(197) GLARGIN+MET, n=105 Bas.HbA1c 8.7 %
MIX25BID+MET 7.8 / 7.4** 0.9 / 1.3** 0.57 / 0.62*** 1.6 / 2.3** 4.75 / 8.27*
Raskin et al (198) GLARGIN+OAD, n=209 Bas.HbA1c 9.8 %
MIX30BID+OAD 7.41 / 6.91** 2.36 / 2.79** 51 / 79* 3.5 / 5.4** 0.7 / 3.4**
Jacober et al† (199) GLARGIN+OAD, n=60 Bas.HbA1c 9.2 %
MIX BID+OAD 7.34 / 7.08** 0.75 / 1.0**
0.28 / 0.35**
28 / 37** 1.52 / 1.98 (NS) 10.7 / 2.8*
Holman et al (200) DETEMIR+OAD, n=469 Bas.HbA1c 8.5 %
MIX30BID+ OAD 7.6 / 7.3*** 0.8 / 1.3*** 0.53 / 0.49
42 / 48 (NS) 1.9 / 4.7** 0 / 3.9**
ID=Insulin dose. Bas HbA1c, Baseline HbA1c (mean of both study groups).
*p<0.05; **p<0.01; *** p<0.001; NS, not significant; ND, not documented. OD, once daily; BID, twice daily; TID, three times a day.
† Cross-over study. Hypoglycemia: Events/patient-year (% of patients). OAD, oral antidiabetic drug
2.2.3 InsulIn
Choice of the insulin regimen
Studies comparing basal insulin with OAD to mixed insulin with OAD are shown in Table 2 and studies comparing basal insulin with OAD to mixed insulin without OAD in Table 3. The comparison of studies using basal insulin with OAD and multiple injections with OAD is shown in table 4.
In the various comparisons there was no difference in glycemic control except in studies where the insulin doses differed significantly (table 2-4). Weight gain was significantly less with basal insulin and OAD than with mixed insulin with OAD (Table 2) or multiple injections with OAD (Table 4) in 5 out of 8 comparisons and not significantly different in the remaining 3 comparisons. Hypoglycemia was also significantly less in 5 out of 8 comparisons with basal insulin and OAD than with mixed or multiple insulin injections combined with OAD. These data support initiation of insulin therapy with the addition of basal insulin to OAD (6).
table 2. Studies comparing basal insulin with OAD to mixed insulin twice daily with similar OAD in insulin- naïve patients with type 2 diabetes. Studies after year 1990 with duration ≥ 3 months are included.
ID=Insulin dose. Bas HbA1c, Baseline HbA1c (mean of both study groups). *p<0.05; **p<0.01; *** p<0.001;
NS, not significant; ND, not documented. OD, once daily; BID, twice daily; TID, three times a day.
† Cross-over study. Hypoglycemia: Events/patient-year (% of patients). OAD, oral antidiabetic drug.
table 3. Studies comparing basal insulin with OAD (oral antidiabetic drug) to mixed insulin without OAD in insulin-naïve patients with type 2 diabetes. Studies after year 1990 with duration ≥ 3 months are included.
ID, Insulin dose; Bas HbA1c, Baseline HbA1c (mean of both study groups); * p<0.05; **p<0.01; ***
p<0.001. NS, not significant. ND, not documented. OD, once daily; BID, twice daily; TID, three times a day. Hypoglycemia: Events/patient-year (% of patients).
Author (Reference) Author (Reference) Author (Reference)
Author (Reference) ComparatorComparator ComparatorComparator ENDHbAENDHbAENDHbAENDHbA1c1c1c1c HbAHbAHbAHbA1c1c1c1c IDIDIDID WeightWeightWeightWeight
Hypoglyce Hypoglyce Hypoglyce Hypoglycemmmmiaiaiaia
Yki-Jarvinen et al (68)
NPHevening+OAD, n=57 Bas. HbA1c 9.8 %
MIX 30 BID 8.0 / / / / 7.9 (NS)
1.9 / / / / 1.8 (NS)
20 / / / / 43
(ND) 1.2 //// 1.8* NS
Yki-Jarvinen et al (68) NPH morning+OAD,
n=61 Bas. HbA1c 9.6 %
MIX 30 BID 7.8 / / / / 7.9 (NS)
1.7 //// 1.8 (NS)
19 //// 43 (ND)
2.2 //// 1.8
(NS) NS
Wolffenbuttel et al (201) NPH evening +SU, n=62
Bas.HbA1c 10.9 %
MIX 30 BID 8.1 / / / / 8.2 (NS)
2.4 / / / / 3.0
(NS) 24 / / / 39* / 4.4 / / / / 4.0
(NS) ND
Wolffenbuttel et al (201) NPH morning+SU, n=67
Bas.HbA1c 11.2 %
MIX 30 BID 8.5 //// 8.2 (NS)
2.6 //// 3.0
(NS) 26 //// 39* 3.4 / 4.0
(NS) ND
Janka et al (202) GLARGIN evening+OAD, n=364
Bas.HbA1c 8.8 %
MIX 30 BID 7.15 ////
7.49***
1.64 ////
1.31***
28.2 //// 64.5 (ND)
1.4 //// 2.1
(NS) 2.6 //// 5.7***
table 4. Studies comparing basal insulin and OAD to multiple preprandial injections with similar OAD in insulin-naive patients with type 2 diabetes.
**p<0.01; *** p<0.001; NS, not significant; ND, not documented. OD, once daily; BID, twice daily; TID, three times a day. OAD, oral antidiabetic drug. BasHbA1c; Baseline Hba1c (mean of both groups). Hypoglycemia:
events/patient-year.
Practical aspects of initiation of insulin therapy
Although insulin therapy has many beneficial effects, reluctance to initiate insulin is still common. This is in part because of lack of time and resources. There is thus a need to develop innovative strategies to facilitate the transition to insulin therapy. As discussed above, simple addition of basal insulin to existing oral agents is an attractive way to start insulin therapy as it involves only one injection of insulin, the dose of which can be adjusted based on self-monitoring of fasting plasma glucose (8), (12), (15), (68). Historically, insulin therapy has been started individually in patients with type 2 diabetes. Considering limited resources, the large numbers of patients, it would seem worthwhile to establish whether insulin can be started in groups. There are, however, no studies comparing initiation of insulin individually as compared to groups.
Author (Reference) Comparator ENDHbA1c
(%) HbA1c
(%)
IU (IU/kg,
IU/day) Weight (kg)
Hypo- glycemia Landstedt-Hallin et al
(203) NPH+SU, n=80 Bas. HbA1c9.1 %
PREPRANDIAL TID+SU
7.5/7.1 (NS)
1.7/2.1 (NS)
26/29 (NS)
1.9/3.4
**
ND
Bastyr et al (204) NPH+SU, n=91 Bas. HbA1c10.2 %
PREPRANDIAL TID+SU
8.5/7.7
**
1.89/2.33 (NS)
0.29/0.42 (ND)
2.3/3.4 (NS)
7.3/13.3 (NS)
Holman et al (200) DETEMIR+SU+MET,
n=475 Bas. HbA1c 8.5 %
PREPRANDIAL TID+SU+MET
7.6/7.2
***
0.9/1.3
***
0.49/0.61
**
1.9/5.7
***
grade 2
***
Bretzel et al (205) GLARGIN+OAD, n=418
Bas. HbA1c 8.7 %
PREPRANDIAL TID+OAD
7.0/6.8 (NS)
1.7/1.8 (NS)
42/45 (ND)
3.0/3.5 (NS)
4.2/13.5
***
3. AIMS oF THE STUDY
I. To determine the effect of insulin therapy on LFAT content and hepatic insulin sensitivity in patients with type 2 diabetes.
II. To determine the effects of addition of rosiglitazone to insulin on hepatic sensitivity to insulin, insulin requirements and glycemic control in patients with type 2 diabetes treated with high insulin doses.
III. To compare the effect of adding nateglinide or placebo on postprandial glucose excursions in patients treated with basal insulin and metformin.
Iv. To determine whether insulin can be started equally well individually and in groups.
4. SUBJECTS AND STUDY DESIGNS
4.1. subjects
Baseline characteristics of the study subjects are shown in Table 6. For studies I and IV, insulin-naive patients with type 2 diabetes who were poorly controlled with oral antidiabetic drugs, MET alone (I) and MET and/or SU (IV) were recruited. For study II, patients with type 2 diabetes who had been treated with stable doses of MET, and were poorly controlled despite of high insulin dose were recruited. For study III patients with type 2 diabetes treated with basal insulin therapy and MET were studied.
Subjects were included based on the following criteria: 1) age over 18 years, 2) HbA1c between 7.0 and 12 % (IV) or ≥ 6.5 % (III), 3) body mass index between 20–50 kg/m2 (III), less than 45 kg/m2 (IV) and stable body weight and glycemic control for at least 6 months prior to participation (I, II). Further inclusion criteria were willingness to perform self-monitoring of blood glucose (III, IV) and to share some health information with other members of the group (IV).
In study III the inclusion criterion for entering the treatment period was an HbA1c between 6.5 and 9.0 %. Moreover, subjects with non-compliance as determined from failure to perform any diurnal glucose profiles during the optimization period were excluded from this study.
Exclusion criteria were clinical evidence of symptomatic cardiovascular or liver or other severe disease as determined by medical history, physical examination and standard laboratory tests (blood counts, electrolytes, creatinine, urine sample, electrocardiogram). Further exclusion criteria were treatment with drugs likely to interfere with glucose tolerance, macroalbuminuria, proliferative retinopathy, excessive alcohol consumption (>20 g/day), drug abuse and pregnancy (I-IV).
In addition, a history of ketoacidosis or positive GAD-antibodies or liver enzymes (S-ALT, S-AST; S-ALP) higher than 3 times the upper limit of normal or night shift work were exclusion criteria in studies III and IV.
For the study II subjects underwent transthoracic echocardiography and left ventricular ejection fraction equal or less than 50 % or any other clinically significant abnormality was an exclusion criteria.
Written informed consent was obtained from all subjects. The protocols were approved by Ethics Committee of Helsinki University Central Hospital (I-IV). Study III was also approved by local ethics committees of each participating center outside Helsinki.
4.2. study desIgn
Effect of insulin therapy on LFAT and hepatic insulin sensitivity in patients with type 2 diabetes (I)
Fourteen patients with type 2 diabetes treated with MET (2 g/day) alone were recruited and metabolic studies were performed before and 7 months after the initiation of basal insulin. Metabolic studies included measurements of LFAT, whole body and hepatic insulin sensitivity (fig. 3), intra-abdominal (IA) and subcutaneous (SC) fat volumes, the percentage of body fat and glucose and lipid oxidation rates. Fasting blood samples were obtained for measurements of glucose, insulin, ALT, FFA, adiponectin, and blood lipid concentrations.
Effect of addition of rosiglitazone to insulin on LFAT and heptatic insulin sensitivity (II)
Fourteen patients with type 2 diabetes (9 men and 5 women) were enrolled by contacting specialists in Southern Finland. These patients had had a stable and high insulin dose in addition to 2 g of MET for at least 2 years. Despite of high-dose insulin therapy (range 115-400 IU/day) their glycemic control was unsatisfactory. LFAT, fat distribution, fat free and fat mass, whole body and hepatic insulin sensitivity (fig. 3) and rates of substrate oxidation were determined during insulin and MET treatment and 8 months after addition of rosiglitazone (8 mg/day).
Effect of adding nateglinide or placebo on postprandial glucose excursions in type 2 diabetic patients treated with basal insulin and MET (III)
Study III was an investigator-initiated multicenter, double-blind, randomized, parallel-group, fixed dose trial. The efficacy, safety and tolerability of nateglinide were compared to placebo in patients with type 2 diabetes treated with the combination of basal insulin and MET (2 g/day). Basal insulin was first titrated to optimize glucose control during a 24-week period (optimization period). The goal was to achieve a mean FPG of 4.0–5.5 mmol/l. Thereafter either nateglinide or placebo was added before main meals for 24 weeks (treatment period). Study was performed at five sites in Finland. During first 24-week period basal insulin (NPH or glargine) was titrated to optimize glucose control. At the beginning of the treatment phase eligible patients (n=81) were randomly assigned to treatment with nateglinide or placebo using minimization of differences between the treatment groups (206). The following variables(relative weight of each variable is given in parentheses) wereconsidered: age (1x); gender (0.5x); body mass index (1.5x); HbA1c (1.5x), durationof diabetes (0.5x); duration of insulin therapy (1.0x); type of basal insulin (NPH or glargine) (1.5x) and use of diuretics or ß-blockingagents (0.25x) (206). Randomization was carried out at the Helsinki University Central Hospital.
Patients measured FPG every morning and performed a diurnal profile with plasma glucose measurements once during weeks –24, -12, -8, -4, -2 and 0, 2, 4, 8, 12, 16, 20, and 24. The visits and phone calls during the study weeks are shown in the fig. 1.
At weeks -12, 0, 12 and 24 the measurements of HbA1c, blood count, electrolytes, and serum lipid concentrations were performed. Safety laboratory tests included measurement of S-ALT, creatinine and bilirubin at weeks -2, 0, 2, 24.
Figure 1. Design (III). Effect of adding nateglinide or placebo on postprandial glucose excursions in type 2 diabetic patients treated with basal insulin and MET. Visits at weeks -24, -12, -2, 0, 2, 12 and 24. Phone calls at weeks -22, -20, -16, -8, -6, -4, 4, 6, 8, 16, 20 and 22.
Initiation of insulin therapy individually or in groups (IV)
This study was an investigator-initiated, open, randomized, and parallel-group multi- center study. We compared the initiation of insulin in groups vs. individually in insulin- naive patients with type 2 diabetes. They were poorly controlled on OAD. The study consisted of a 3 to 14-week run-in phase and a 24-week treatment phase. Study groups were in Finland, Sweden, and U.K.
The participants (n= 121) were treated with combination of MET and SU or either drug alone for at least 6 months before the initiation of insulin therapy. The study was performed as the intent-to-treat basis. Week 0 visit the participants were taught how to inject insulin, use the insulin pen, and self-adjust insulin dose. Symptoms and signs of hypoglycemia were discussed. Treatment satisfaction was assessed by asking the patients to fill a Diabetes Treatment Satisfaction Questionnaire DTSQ form (207).
This questionnaire was filled in the beginning and the end of the study.
The randomization to either group or individual education was performed centrally, using the method of minimization of differences (206). The group size was 4–8 subjects
(mean 5.3 persons). Patients performed self-monitoring of FPG every morning and sent FPGs using a modem or by mail before calling the study center. During the call, the study nurse reviewed glucose measurements received at a website (www.prowellness.
com), encouraged self-adjustment of the insulin dose, and asked for possible adverse events, incidents of hypoglycemia, and possible changes in medication. The educational content is shown in table 5. The study design is shown in the Fig. 2. HbA1c, FPG and body weight were measured at every visit. Time spent by a nurse on education, physician’s time, and number and duration of phone calls were recorded. The insulin dose, symptoms and signs of hypoglycemia were recorded at every contact during the study, and treatment satisfaction at week 0 and 24. Measurements of blood count, electrolytes, creatinine, and S-ALT were performed at screening visit -14 to -3, 24 weeks. Serum lipid concentrations were measured at weeks 0, 24.
figure 2. Design (IV). The initiation of insulin therapy individually or in groups. Visits at 0, 6, 12 and 24 weeks, phone calls at 1, 2, 4, 8, 16 and 20 weeks.
MET SU + insulin, individual
MET SU + insulin, group
Run-in period
MET
SU
1 8 16 24
Visit
Phone * * * * * * *
table 5. The educational content (IV).
Visit (wks) Visit (wks) Visit (wks) Visit (wks)
ContentContentContentContent
-2
Home-glucose monitoring.
Pathogenesis of type 2 diabetes Treatment of type 2 diabetes
0
Why and when is insulin therapy needed Injection of insulin
Self-adjustment of the insulin dose
Hypoglycemia (causes, symptoms, treatment)
+6 +12
Weight gain and insulin therapy Targets of the glycemic control Type 2 diabetes and complications Why do insulin vary between patients
+24
Special situations and insulin therapy (missed injection, acute illness, travel)
Encourage to self-adjustment of the insulin dose
